The present invention and embodiments thereof relate to a method for transmitting a signal of a base station in a wireless communication system using a carrier merge. The method includes transmitting to a terminal a Physical Downlink Shared CHannel (PDSCH) on a downlink secondary cell and a Physical Downlink Shared CHannel (PDSCH) indicating the PDSCH on a downlink primary cell; and receiving a reception acknowledgement response on the PDSCH, which is transmitted from the terminal to an uplink primary cell. The PDSCH is transmitted when the downlink secondary cell becomes available, and the transmission timing of the reception acknowledgement response is determined by one of the PDSCH transmission timing or the PDCCH transmission timing.